1. Field of the Invention
The present invention concerns in general improved techniques relating to a pedestrian protection apparatus for a vehicle, an installation structure of a leg sweep member, a front structure of a vehicle, and a bumper of a vehicle. The invention concerns in particular such improved techniques in which occurrence of damages to the vehicle upon a so-called light collision (which will be defined below) is prevented while protecting a leg portion of a pedestrian collided (contacted) with a front end of the vehicle.
2. Discussion of Related Art
In vehicles such as automobiles, there are conventionally disposed bumpers at a front end and a rear end of the vehicle for mainly absorbing impact energy generated upon collision and protecting a vehicle body and passengers. In recent years, a pedestrian protection apparatus is provided at a front of the vehicle so as to be disposed inside of the bumper or disposed independently of the bumper, for protection of the pedestrian when the pedestrian collided with (contacted) the front end of the vehicle.
As well known, the pedestrian protection apparatus includes a leg sweep member having a breadth or width dimension that is substantially the same as the vehicle width and enhanced rigidity so as to exhibit a relatively large degree of strength with respect to a load in a vehicle length or longitudinal direction (in a frontward and backward direction of the vehicle). In general, the leg sweep member is disposed inside of a lower part of a bumper cover of a bumper attached to the front end of the vehicle, more specifically, the leg sweep member is disposed inside of a part of the bumper cover which corresponds to a height position of a part of the leg portion of the pedestrian that is below a knee, so as to protrude in a frontward direction of the vehicle. The thus disposed leg sweep member is fixedly secured by bolts or the like to a structural member which is located at a lower part of the front of the vehicle. For instance, the leg sweep member is secured to a portion of a frame such as a radiator support or a cross member, or a portion of a body panel located at a lower part of the front of the vehicle.
In the thus constructed pedestrian protection apparatus, when the pedestrian collides with or comes into contact with the front end of the vehicle, the leg sweep member is arranged to sweep or scoop the leg portion of the pedestrian below the knee, causing the pedestrian to fall down or to be thrown over toward the vehicle. Accordingly, it is possible to advantageously limit a bending-angle of the knee in an unnatural or undesirable direction upon contact of the pedestrian with the vehicle, thereby minimizing occurrence of injuries to the knee such as bone fractures and assuring protection and safety of the pedestrian.
In the conventional pedestrian protection apparatus described above, however, the leg sweep member with relatively high rigidity is partially connected by bolts or the like to the vehicle structural member. When the impact energy larger than that in collision with the pedestrian is input to the leg sweep member upon a so-called a light or insignificant collision in which the vehicle collides, at a relatively low speed, with a sturdy object having a larger weight than the pedestrian, the leg sweep member may be considerably deformed or bent and contacts neighboring components, devices, equipment and the like, giving damages to those components, devices and so on. In addition, since the leg sweep member is disposed at the lower part of the front of the vehicle, the cooling equipment such as a radiator disposed in the vicinity of the lower part may be damaged by the leg sweep member. In this instance, even in a case of the light collision in which damages to the vehicle body is not so much, the vehicle may suffer from considerably serious damages such as inability to run.
In the light of the above, JP-A-2004-203183 discloses, as a technique to solve the aforementioned problems, a vehicle front structure constructed as follows: Namely, the leg sweep member is fixed to the vehicle structural member by suitable clips or the like. Upon inputting of the load larger than that in collision with the pedestrian, the clips are fractured, thereby releasing fixation of the leg sweep member to the structural member.
The above-indicated publication JP-A-2004-203183 teaches the following effect achieved by the structure descried above: When the pedestrian collides with the front end of the vehicle, the leg sweep member remains fixed to the vehicle structural member and advantageously exhibits its leg sweeping function, thereby assuring protection of the pedestrian collided with the vehicle. Further, in the event of the above-indicated light collision of the vehicle at its front end, the leg sweep member is separated from the front of the vehicle, so that the components, the devices and the equipment disposed at the front of the vehicle are effectively prevented from being damaged due to contact thereof with the leg sweep member.
The inventor of the present invention conducted various experiments relating to such a conventional front end structure of the vehicle and found that it is actually difficult in the conventional technique described above to reliably release the leg sweep member from the vehicle structural member upon the light collision of the vehicle at its front end while keeping the leg sweep member fixed to the structural member upon collision between the pedestrian and the front end of the vehicle.
Described more specifically, a pedestrian collision test was performed on the supposition of a collision of a pedestrian with a front end of a vehicle in which a pedestrian protection apparatus having a leg sweep member was disposed at a front of the vehicle, and there was examined a change with the elapse of time in a load inputted, upon the collision of the pedestrian with the vehicle, to one of fixing portions of the leg sweep member at which the leg sweep member was fixed to the vehicle structural member, which one fixing portion was the closest to a position of the front end of the vehicle against which the pedestrian has hit upon the collision. Further, the inventor performed a light collision test on the supposition of a light or insignificant collision of an obstacle with the front end of the vehicle, and there was examined a change with the elapse of time in a load inputted, upon the collision of the obstacle with the vehicle, to one of fixing portions of the leg sweep member at which the leg sweep member was fixed to the vehicle structural member, which one fixing portion was the closest to a position of the front end of the vehicle against which the obstacle has hit upon the collision. The results of the examinations are indicated in the graph of FIG. 15.
In the pedestrian collision test, there was used, as a test vehicle, a vehicle in which a front bumper was disposed at its front end and the leg sweep member was disposed inside of a synthetic-resin-made bumper cover of the front bumper, such that the leg sweep member was fixed to a radiator support at six points substantially equally spaced apart from each other in the vehicle width direction. A dummy having a weight of 14 kg was collided with a forward end of the front bumper of the test vehicle at a speed of 40 km/h. In the light collision test, a test vehicle similar to that used in the pedestrian collision test was run at a speed of 16 km/h and was collided, at the forward end of the front bumper, with a concrete wall having a weight of 1.5 t. In the pedestrian collision test, the dummy was collided with a substantially middle portion of the forward end of the front bumper in the vehicle width direction. In the light collision test, the test vehicle was collided with the concrete wall at one of opposite end portions of the forward end of the front bumper in the vehicle width direction.
As apparent from the graph of FIG. 15, while there is—a large time difference between a point of time when the load inputted to the fixing potion of the leg sweep member to the vehicle structural member reaches a maximum value in the pedestrian collision and a point of time when the load inputted to the fixing portion of the leg sweep member to the vehicle structural member reaches a maximum value in the light collision, it is recognized that the maximum value of the load in the pedestrian collision and the maximum value of the load in the light collision are substantially equal to each other, namely, about 4800 N. This fact clearly indicates that the maximum value of the load inputted to the leg sweep member in the event of the collision between the pedestrian and the front end of the vehicle and the maximum value of the load inputted to the leg sweep member in the event of the light collision of the vehicle at its front end are substantially equal to each other. Accordingly, it is impossible or considerably difficult to judge, upon occurrence of a collision accident at the vehicle front end, whether the collision is the pedestrian collision or the light collision, on the basis of the magnitude of the load inputted to the leg sweep member.
Therefore, it can be clearly recognized from the above that it is considerably difficult to release the leg sweep member from the vehicle structural member and separate the leg sweep member from the front of the vehicle, in agreement with a timing of occurrence of the light collision of the vehicle at its front end, even if the leg sweep member is arranged to be released from the structural member upon inputting of an impact load larger than that in the collision with the pedestrian, as taught by the conventional technique. Accordingly, the conventional technique mentioned above does not sufficiently attain both of protection of the leg portion of the pedestrian collided with the front end of the vehicle and prevention of occurrence of damages to the vehicle due to the light collision of the vehicle at its front end.